Table Of ContentJEpidemiol 2010;20(1):40-45
doi:10.2188/jea.JE20090062
Original Article
fl
Factors In uencing Participation Rate in a Baseline Survey
of a Genetic Cohort in Japan
Megumi Hara1, Yasuki Higaki1,2, Takeshi Imaizumi1, Naoto Taguchi1, Kazuyo Nakamura1,
Hinako Nanri1, Tatsuhiko Sakamoto3, Mikako Horita1, Koichi Shinchi4, and Keitaro Tanaka1
1DepartmentofPreventiveMedicine,FacultyofMedicine,SagaUniversity,Saga,Japan
2LaboratoryofExercisePhysiology,FacultyofSportsandHealthScience,FukuokaUniversity,Fukuoka,Japan
3FukuokaPrefecturalGovernment,AsakuraHealthWelfareEnvironmentOffice,Asakura,Fukuoka,Japan
4DivisionofInternationalHealthandNursing,FacultyofMedicine,SagaUniversity,Saga,Japan
ReceivedApril14,2009;acceptedJune12,2009;releasedonlineNovember7,2009
ABSTRACT
Background: Although many studies have examined factors that influence the response to postal questionnaires,
fewhave addressed baseline recruitment for cohortstudiesinvolving geneticanalyses. The aim ofthisstudy wasto
describe the method used for a baseline survey, the Japan Multi-institutional Collaborative Cohort Study (J-MICC
Study), in Saga Prefecture, and to examine the factors that might influence the recruitment of participants in such
studies.
Methods: The Saga J-MICC Study is an ongoing population-based prospective cohort study of the genetic and
environmental interactions associated with lifestyle-related disease. From 2005 through 2007, a total of 61447
residents between the ages of 40 and 69 were invited by mail to participate in this study. The survey date and time
were arranged by telephone.
Results: Amongthatpopulation,31002(50.5%)respondedand12078(19.7%)agreedtoparticipate.Acompleted
questionnaire and blood pressure and anthropometric data were collected from all participants; blood, DNA
specimens, and accelerometer measures were obtained from the great majority of them. Female sex and older age
wereassociatedwith ahigherparticipation rate.Inaddition, theconvenienceofthesurvey location andthesending
of a reminder significantly improved the participation rate (odds ratio, 1.3).
Conclusions: Our findings suggest that making the survey location as convenient as possible and sending a
reminder can both substantially improve participation rate in population-based studies.
Key words: population-based study; survey methodology; response rate; participation rate; reminder
defined by local governments, 2) participants in health
INTRODUCTION
checkups conducted by local governments, 3) visitors to
In 2005, we began a population-based prospective cohort health checkup facilities, and 4) visitors to a cancer hospital.1
study in Saga Prefecture, located in the north of the island of The target number of study subjects was set at 100000
Kyusyu, as part of the Japan Multi-institutional Collaborative throughout Japan, and each study group is expected to enroll
Cohort Study (J-MICC Study), which aims to assist in the more than 5000 participants.
prevention of cancer and other life-style related diseases by In our study (designated the Saga J-MICC Study), we
obtaining fundamental data on genetic traits associated with planned to recruit approximately 10000 volunteers from
these diseases.1 The J-MICC Study is a union of independent residents of Saga City, which had a population of 167000 as
cohort studies that are conducted by the Cohort Study of September 2005. All candidates were enrolled from the
Executing Groups (10 groups, including the J-MICC Study, residentregisterandwereinvitedbymailtoparticipateinour
as of April 2008) and is coordinated by the J-MICC central baseline survey, which was arranged by us, completely
officeattheNagoyaUniversityGraduateSchoolofMedicine. independent of the health checkup program conducted by
The sources of study subject recruitment depend on each thelocalgovernment.Herein,weshalldescribethemethodof
study group, and include 1) volunteers residing in areas the baseline survey and identify the factors that affect
Addressfor correspondence. Dr.MegumiHara,PreventiveMedicine,SagaUniversity,Nabeshima 5-1-1,Saga,Saga 849-8501, Japan(e-mail:harameg@cc.
saga-u.ac.jp).
Copyright©2009bytheJapanEpidemiologicalAssociation
40
HaraM,et al. 41
participation rate in a community setting. Although many longertraveltime;theother2locationswereratherdifficultto
multicenter prospective studies that recruited subjects in locate due to their complicated surroundings.
such a setting have reported their study design and the Candidates were enrolled after confirming their name, sex,
characteristics of participants,2–7 few have reported details of date of birth, and address on the resident register at the city
the participation rate with respect to methodological factors office. At 1 month before the survey, an invitation letter
suchastheconvenienceofthesurveylocationandthesending containing an explanation of the study, a schedule of the
of a reminder to participants.8–10 baseline surveys at each study area, and a request for
participation was sent to the selected subjects. Subjects were
asked to reply by mail or facsimile to indicate whether they
METHODS
chose to participate in the study or not. Two weeks after the
Study subjects and recruitment first contact, a reminder was sent to the subjects who had not
On October 1, 2005, the population (and area) of Saga City responded, in all but 1 study area. Reminders could not be
effectively increased from 167000 (104km2) to 207000 sent to about 40% of the candidates in 1 western area
(355km2) because of the administrative consolidation of 3 (Nabeshima) where the last surveys had been conducted,
towns and 1 village. Our university, the Saga University because 1 person had strongly complained to city officials
FacultyofMedicine,islocatedinthenorthwesternpartofthe abouttheirgrantinguspermissiontousepersonalinformation
former Saga City. We decided to recruit study subjects from in the register, which resulted in him receiving the initial
residents of the former Saga City because arranging survey invitation letter and a reminder. Accordingly, those city
locations outside this area was rather difficult, due to the officials requested that we not send any additional reminders.
considerable distance between such locations and the A schedule of the days of the investigation was arranged
university. The former Saga City consisted of 19 that were by telephone with all subjects who chose to participate.
administratively demarcated to ensure that children could A self-administered questionnaire was sent to the participants
conveniently attend a public elementary school within each beforehand and they were instructed to bring their completed
area; a public hall islocated near each elementary school and questionnaires to the study site. The questionnaire included a
these halls were utilized for the baseline survey. Eligible survey of sleeping and exercise, alcohol drinking, smoking,
subjects included all residents between the ages of 40 and 69 psychologicalstress,medicationandsupplements,foodintake
years living in the above 19 areas; those who could not frequency, family disease history, past disease history, and
complete the questionnaire survey or did not give consent female reproductive history.
to be followed up were excluded. The corresponding target
population was approximately 62000. Assuming a Baseline survey
participation rate of 20%, about 12000 residents were Participants gathered in a survey location in each area on the
expected to participate. day of investigation. Researchers, who were all medical
The study protocol of the overall J-MICC Study was doctors,orallyexplainedthepurpose,contents,andconditions
approved by the Ethics Committee at Nagoya University of cooperation of the study, using PowerPoint slides and
Graduate School of Medicine1; the Saga J-MICC Study was documentsconcerningthestudy;aboutfourtofive30-minute
approved by the Ethics Committees of both Saga University explanationsessionswereheldperdayand,ateachsession,1
Faculty of Medicine and Nagoya University Graduate School doctor was assigned to explain the study to each group of
of Medicine. The baseline survey was conducted from approximately10to15subjects.Informedconsentformswere
November 1, 2005 through December 22, 2007. For the signedbyallsubjectswhoagreedtoparticipate,andtheforms
purposeofconvenience,thesurvey periodwasdividedinto5 were all individually checked by either the doctor-in-charge
phases(November2005toMarch2006forthesurveyofthe3 or research nurses. Then, after inspection of the completed
northernareas,April2006toSeptember2006forthe5eastern questionnaires by research nurses, the participants’ blood
areas, October 2006 to March 2007 for the 4 southern areas, pressure (systolic and diastolic) and anthropometric
April 2007 to August 2007 for the 4 central areas, and characteristics (height, weight, body fat%, and waist and hip
September 2007 to December 2007 for the 3 western areas). circumferences) were measured. A 21-mL blood sample was
The baseline survey took place during the day, usually on 2 collected from each participant, using two 6-mL plain tubes
weekdays and 1 weekend, in a public hall within each study for serum, a 7-mL tube with EDTA-2Na for plasma and the
areaandatotherhallsavailablewithinoroutsidethearea.The buffy coat, and another additional 2-mL tube with EDTA-2K
surveylocationswerechosensothattheywouldbeasnearas forwholeblood.Wesent1.1mLofserumand2mLofwhole
possible to the residential areas of participants, so that they bloodtoanexternaltestinglaboratory(SRL,Tokyo,Japan)to
could be easily located by participants. However, such a determine levels of total protein, albumin, triglyceride, total
location was not available in 3 study areas, which were cholesterol, HDL cholesterol, aspartate aminotransferase,
classified as “inconvenient” locations. One such location was alanine aminotransferase, γ-glutamyl transpeptidase, uric
outsideanddistantfromthestudyarea,andthereforerequired acid, creatinine, hemoglobin A1c, and the serostatus of
J Epidemiol 2010;20(1):40-45
42 Participation intheJ-MICC Study
hepatitis B surface antigen and antibody to hepatitis C virus. and thus remain unknown. Consequently, 12078 subjects
Within 3 hours, the remaining samples were divided into participated in this cohort study between November 1, 2005
eighteen0.3-mLtubes(8forplasma,2forthebuffycoat,and and December 22, 2007 (participation rate: 19.7%; Figure 1).
8 for serum) and a 1.5-mL tube (for serum) and stored at Table 1showstheresponseratesandparticipationrates,by
−80°C. Half of the blood samples, except the 1.5-mL tube, sex,age,andtheconvenienceofthesurveylocation.Boththe
were sent to the J-MICC central office. Participants who response and participation rates were significantly higher
agreed to allow measurement of their daily physical activities among women than men (OR, 1.3). The rates increased with
wore an accelerometer (Lifecorder; Suzuken Co., Ltd., age:theORforresponseinthe65–69agegroup,ascompared
Nagoya, Japan) for 10 days, after which they returned them with that in the 40–44 age group, was 2.6 (95% CI 2.5–2.8),
by mail. andthecorrespondingORforparticipationwas2.0(1.9–2.2).
The convenience of survey location was also associated with
Analyses both rates, and in subjects with a convenient location, there
The response rate was defined as the ratio of the number of
respondents (those who indicated whether they would
participate in the study or not) to the number of candidates 61,447
(those who were invited by mail to attend the study). The Subjects invited
to attend
participation rate was obtained by dividing the number of
participants(thosewhoultimatelyparticipated)bythenumber
of candidates. The response and participation rates were
30,445
compared by sex, 5-year age, convenience of the survey 31,002
Did not
location,andthereceiptofareminder.Oddsratios(ORs)and Responded
respond
their 95% confidence intervals (CIs) for the response or
17,926
participation with respect to these factors were calculated as
Refused
measuresofthestrengthofassociation.Whenthe95%CIsdid
to participate
not include unity, the corresponding ORs were considered
13,076
statistically significant if P was less than 0.05. Declared intention
to participate
998
RESULTS
Canceled
In total, 61447 residents of the 19 study areas in Saga City participation
wereinvited toparticipate intheSagaJ-MICC Study.Of that 12,078 49,369
population, 31002 indicated whether they would participate Participants in baseline Non-participants in
survey baseline survey
or not (response rate, 50.5%). Although 13076 subjects
indicated an intention to participate, 998 of these ultimately Figure 1. Number of respondents and participants in the
canceled;theexactreasonsforcancellationwerenotaskedfor SagaJ-MICC Study
Table 1. Response and participation rates in the Saga J-MICC Study, by sex, age group, and the convenience of the survey
location
Invited Respondents Oddsratio Participants Oddsratio
Variable
subjects No.(%) (95%CI) No.(%) (95%CI)
Total 61447 31002(50.5) 12078(19.7)
Sex
Male 29007 13549(46.7) 1(reference) 5081(17.5) 1(reference)
Female 32440 17453(53.8) 1.33(1.29–1.37) 6997(21.6) 1.29(1.24–1.35)
Ageatinvitation(years)
40–44 9744 3909(40.1) 1(reference) 1491(15.3) 1(reference)
45–49 10108 4334(42.9) 1.12(1.06–1.19) 1531(15.1) 0.99(0.91–1.07)
50–54 11082 5212(47.0) 1.33(1.25–1.40) 1944(17.5) 1.18(1.09–1.27)
55–59 12750 6596(51.7) 1.60(1.52–1.69) 2458(19.3) 1.32(1.23–1.42)
60–64 9317 5580(59.9) 2.23(2.10–2.36) 2401(25.8) 1.92(1.79–2.07)
65–69 8446 5371(63.6) 2.61(2.46–2.77) 2253(26.7) 2.01(1.87–2.17)
Surveylocationa
Inconvenient 9500 4610(48.5) 1(reference) 1591(16.7) 1(reference)
Convenient 49743 25703(51.7) 1.13(1.09–1.19) 10129(20.4) 1.27(1.20–1.35)
aInevaluatingtheassociationwiththeconvenienceofsurveylocation,2204subjectstowhomreminderscouldnotbesentwereexcluded.
CI:confidenceinterval.
J Epidemiol 2010;20(1):40-45
HaraM,et al. 43
Table 2. ResponseandparticipationratesamongresidentsofNabeshimawhodidordidnotreceiveareminder
Invited Respondents Oddsratio Participants Oddsratio
Variable
subjects No.(%) (95%CI) No.(%) (95%CI)
Total 5139 2174(42.3) 970(18.9)
Reminder(−)a 2204 689(31.3) 1(reference) 365(16.6) 1(reference)
Reminder(+) 2935 1458(50.6) 2.17(1.93–2.44) 605(20.6) 1.31(1.13–1.51)
aReminderscouldnotbesenttothesesubjects,duetoacomplaintfromaresident,asdescribedintheMethods.
CI:confidenceinterval.
Table 3. CharacteristicsofparticipantsinthebaselinesurveyoftheSagaJ-MICCStudy
Invited Participants Bloodprovided DNAprovided Accelerometerdata
subjects (%)a (%)b (%)b provided(%)b
Total 61447 12078(19.7) 12072(99.9) 12041(99.7) 12020(99.5)
Men 29007 5081(17.5) 5079(99.9) 5063(99.6) 5054(99.5)
40–44 4625 569(12.3) 568(99.8) 563(98.9) 566(99.5)
45–49 4776 591(12.4) 591(100) 591(100) 586(98.2)
50–54 5354 794(14.8) 793(99.9) 791(99.6) 788(99.2)
55–59 6120 1048(17.1) 1048(100) 1044(99.6) 1044(99.6)
60–64 4282 1027(24.0) 1027(100) 1025(99.8) 1022(99.5)
65–69 3850 1052(27.3) 1052(100) 1049(99.7) 1048(99.6)
Women 32440 6997(21.6) 6993(99.9) 6978(99.7) 6966(99.6)
40–44 5119 922(18.0) 922(100) 922(100) 918(99.6)
45–49 5332 940(17.6) 940(100) 939(99.9) 934(99.4)
50–54 5728 1150(20.1) 1150(100) 1149(99.9) 1145(99.6)
55–59 6630 1410(21.3) 1408(99.9) 1405(99.6) 1405(99.6)
60–64 5035 1374(27.3) 1374(100) 1371(99.8) 1370(99.7)
65–69 4596 1201(26.1) 1199(99.8) 1192(99.3) 1194(99.4)
aPercentagesofproportionstoinvitedsubjects.
bPercentagesofproportionstoparticipants.
was a significantly higher response rate (OR, 1.1) and this rural area is about 4% per year,11 which is relatively low
participation rate (1.3) than for those without such a location. in comparison to urban areas of Japan. Therefore, follow-up
For the purpose of convenience in scheduling the baseline andretention ofstudy participantsisprobablyeasier.Second,
surveys,theNabeshimaareawasdividedinto2,andlettersof this area has a population-based cancer registry,12 the Saga
invitation were sent first to one section and then to the other. Prefectural Cancer Registry, whose data were included in the
Because the reminders could not be sent to residents in the series, Cancer Incidence in Five Continents Vol. VIII.13 This
latter section due to the complaint described in the Methods, registration will be helpful for the detection of cancer
the response and participation rates were compared between development in future follow-up examinations.
these sections (Table 2). The response and participation rates In this baseline survey, the participation rate was 20%,
in the section to which the reminders were sent were which is substantially lower than the rates for population-
significantly higher than those in the section that did not based cohort studies in Japan (81%–95%).3,5,14–16 In such
receive the reminder (ORs for the response and participation: cohort studies, baseline surveys were most frequently
2.2 and 1.3, respectively). arranged in conjunction with periodic health checkups
Allparticipantsprovidedcompletedquestionnaires,aswell conducted by local governments. Blood samples were
asbloodpressureandanthropometricdata.Thegreatmajority donated in 2 such cohort studies, but donation rates were
of them also provided blood (99.9%), DNA specimens onlyapproximately30%.3,5IntheSagaJ-MICCstudy,which
(99.7%), and accelerometer data (99.5%); all gave their wasnotpartofgovernmentalhealthscreening,theparticipants
consent to use these data in the present study (Table 3). hadtotraveltoasurveylocationsolelyforthepurposeofthe
study, and thus the participation rate may be viewed as
relatively high. Several population-based cohort studies,
DISCUSSION
including genetic analyses in foreign countries, reported
The Saga J-MICC Study cohort participants were recruited participation rates of 30% to 78%.4,6,7,10,17,18 Although it is
from community residents in Saga City, a method which has possible that the participation rate is affected by the study
the following advantages. First, the rate of emigration from purpose, we do not know whether the genetic aspect of the
J Epidemiol 2010;20(1):40-45
44 Participation intheJ-MICC Study
presentstudyinfluencedtheparticipationrate.Althoughmany withtheconvenienceofthesurveylocationandthesendingof
studies have examined the factors that influence the response a reminder. Taking both these factors into account may
to postal questionnaires,9,19 few have addressed the baseline improve participation rate in population-based studies that
recruitmentofcohortstudiesinvolvinggeneticanalysis.4,10In include genetic analysis.
this study, female sex and older age were associated with
higher response and participation rates. The European Male
ACKNOWLEDGEMENTS
AgingStudy,whichcollectedDNAspecimensfrommenaged
40–79 years, reported that the participation rate was highest ThechiefinvestigatoroftheJ-MICCStudyisProf.Nobuyuki
among those aged 50–59 years.10 In the Prospect-EPIC Hamajima at the Department of Preventive Medicine/
Utrecht study,theparticipation ratedecreasedwith increasing Biostatistics and Medical Decision Making, Nagoya
age among women aged 50–69 years.4 One possible reason University Graduate School of Medicine, Japan. We, the
forthisdiscrepancyisthat,inthepresentstudy,oldersubjects Saga J-MICC Study, greatly appreciate the participants and
(who were likely to be retirees) and women (who were likely supporting organizations. This study was supported in part
to be housewives) may have been available to attend the by Grants-in-Aid for Scientific Research on the Special
baseline surveys during the daytime on scheduled days. Priority Areasof Cancer(No.17015018),Scientific Research
Although other demographic, socioeconomic, and lifestyle (A) (No. 20249038) and (B) (No. 18390182), and Grants-
factors may be correlated with the participation rate,10,20–23 in-Aid for Young Scientists (A) (No. 20689014) and (B)
such information was not available for nonparticipants in the (No. 18790380) from the Ministry of Education, Culture,
present study. Sports, Science and Technology, Japan.
A main objective of this report was to identify the
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